1. Field of the Invention
The invention relates to a fuel cell and a fuel cell system.
2. Description of the Related Art
Recently, an expectation is mounting highly for a fuel cell as a clean energy not emitting any harmful matter such as sulfur oxide and nitrogen oxide, and various small power supply systems have been proposed for use in an automobile, a household power source, and a portable information appliance. In particular, a direct methanol fuel cell (DMFC) consumes pure methanol or a mixed solution of methanol and water. For this reason, as compared with other types of fuel cells using hydrogen as a fuel, not only handling of a fuel is easier, but also no humidifying mechanism is needed and the operating temperature is low, and thus, a heat control mechanism may be simple. These merits mean that the DMFC is suited as a power source for small appliances. Against such a background, development of the DMFC as a small-sized power supply is being promoted.
For the purpose of supplying an oxidizer to the cathode side and cooling a membrane electrode assembly (MEA), the DMFC is provided with ventilation means, such as a fan, for blowing wind to the cathode side. If ventilation to the cathode side is excessive, however, the MEA is too dried, so that a power generation performance of the MEA deteriorates.
Accordingly, JPA 2003-157879 (KOKAI) incorporated by reference, the entire contents of which are incorporated herein by reference, proposes a fuel cell in which, in order to prevent a cathode gas diffusion catalyst layer of an MEA from being covered with reaction production water at the cathode side, a moisture absorbing evaporation member is externally attached to the cathode side, and wind is blown to the external evaporation member from a fan such that wind does not directly hit the MEA, whereby moisture adhered to the evaporation member is evaporated. In the fuel cell of JPA 2003-157879 (KOKAI), however, the device size is increased since the evaporation member is externally attached to the cathode side, and thus, it is not suited to a small-sized power supply for a portable electronic appliance.